Preliminary observations on the productive response of cvs Vermentino and Chardonnay affected by "Bois noir" in Sardinia

• Published in: Journal of plant pathology Vol. 86; no. 4; p. 320
• Main Authors: Garau, R, Prota, V A, Tolu, G, Sechi, A
• Format: Journal Article
• Language: English
• Published: 01-12-2004
• Subjects: Phytoplasma; Vitis vinifera; Italy, Sardegna
• ISSN: 1125-4653

Surveys carried out in North Sardinia vineyards disclosed differences in the symptomatological reactions of cvs Vermentino and Chardonnay affected by "Bois noir". In particular, 'Chardonnay' showed typical disease symptoms increasing in severity from July to September, while in 'Vermentino', symptoms were milder and began to appear in August. PCR detected phytoplasmas of subgroup 16SrXII-A from June to September in more than 78% of the 'Chardonnay' samples tested, whereas positive reactions were obtained in June and September from 33% of 'Vermentino' vines that had shown symptoms only once over a three year period (1999-2001). However, further testing of symptomatic 'Vermentino' stocks carried out in September 2003, gave a positive response higher that 87%. Analysis of variance of the data relative to sugar content and number of bunches of 50 diseases and 50 apparently healthy Chardonnay vines gave statistically significant differences. A similar analysis of the number of bunches of 'Vermentino' plants that were consistently asymptomatic (18 vines), or had shown symptoms only in 1999 (10 vines), or for several years in a row (17 vines), was not statistically significant. By contrast, differences in the sugar content were significant between 'Vermentino' vines of the third group (consistently symptomatic) and the other two groups separately, but not between vines of the first (consistently symptomless) and second (symptoms in a single year) groups. In infected 'Chardonnay', shrivelled clusters were 30% of the total, and the yield was decreased by ca 58%. These results highlight the clear-cut differential influence of "Bois noir" on the productive parameters of Vitis vinifera cultivars under north Sardinian conditions.